Thigh prosthesis

ABSTRACT

A thigh prosthesis comprises a thigh frame interconnected through a knee-joint mechanism to a crus with a foot. In the thigh frame a stump-receiving sleeve is articulately mounted, having a stump-receiving chamber. The stump-receiving sleeve is kinematically associated with the knee-joint mechanism in such a manner that to each position of the stump-receiving sleeve with respect to the thigh frame corresponds a definite position of the crus.

United States Patent [1 1 Gusev THIGH PROSTHESIS [76] Inventor: LavrentySavinovich Gusev, ul.

Schuseva, 2/19, kv. 29, Kiev,

OTHER PUBLICATIONS Human Limbs & Their Substitutes by Klopsteg &

[451 Apr. 30, 1974 Wilson et a1. McGraw-Hill Book Co., Inc. 1954, pages525-528 relied upon.

Primary Eraminer-Richard A. Gaudet Assistant ExaminerRonald L. FrinksAttorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen 57 ABSTRACT Athigh prosthesis comprises a thigh frame interconnected through aknee-joint mechanism to a crus with a foot. In the thigh frame astump-receiving sleeve is articulately mounted, having a stump-receivingchamber. The stump-receiving sleeve is kinematically associated with theknee-joint mechanism in such a manner that to each position of thestump-receiving sleeve with respect to the thigh frame corresponds adefinite position of the crus.

4 Claims, 4 Drawing Figures THIGH PROSTHESIS This invention relates tomedical engineering and has particular reference to prosthetics and,specifically, thigh prostheses.

At this time, known in the art are a variety of types of thighprostheses, each consisting of a thigh frame or carcass whichaccommodates a stump-receiving chamber. The distal end of the thighframe is connected to the proximal end of the crus through asingle-pivot joint which is essentially a knee-joint mechanismpossessing l of freedom and which provides for passive coupling betweenthe thigh frame and the crus. The distal end of the crus is connected tothe foot so as to form the crural portion of the prosthesis. Themechanism of the knee joint has a retainer to which protects the latteragainst recurvation. in order to provide rotative motion of the cruralportion during walking, the prosthesis is fitted with a knee-foldingdevice formed of, for example, a rubber pull-piece or a spring-actuatedknee-folding device of any conventional design.-

In the so-called patient-prosthesis system, the prosthesis is generallydesigned as a mechanism possessing 2 of freedom, Le, a double flatpendulum composed of physical pendulums, for example, the upper leg orthigh portion and the lower leg or crural portion.

Oscillations of the thigh portion (thigh frame) in the sagittal planeabout a fixed axis passing through the center of the hip joint head,result from the active forces of the thigh stump which are applied tothe thigh frame (i.e., to the walls of the stump-receiving chamber) anddue to its own weight, and with the frequency and amplitude ofoscillations thereof being under control of the patients CNS (centralnervous system).

Oscillations of the crus in the sagittal plane, with respect to thehorizontal axis passing through the fulcrum of the knee-joint mechanism,result from the forces of inertia that arise due to the oscillatingmotion which is performed by the fulcrum axis of the knee-jointmechanism, as well as from the action of gravitational forces and theelastic forces of the knee-folding device.

However, the period and amplitude of the crus oscillations with respectto the thigh frame cannot be readily controlled by the patients CNS.

Another disadvantage which is inherent in the known prosthesis residesin the passive coupling between the thigh frame and the crus whichprevents the patient for effecting a direct and a back coupling betweenhimself and the crural portion of the prosthesis so as, to ensure thatthe oscillations of the crus depend upon those of the thigh frame.Additionally, the passive coupling excludes the formation of a presetmotional behaviour of the crus in dependence upon the rhythm andcharacter of walking, in effect, makes it impossible to provide,symmetric motion of the prosthesis members with respect to the other(unaffected) lower extremity. A further disadvantage of the knownprosthesis lies in the presence of two degrees of freedom in theprosthesispatient system, which prevents the formation of a rather highstability of the knee-joint mechanism against spontaneous swinging atthe moment of support, and entails an increased consumption of thepatients intrinsic energy which must bespent for coordination of motionsduring prosthesis-aided walking, and also necessitates the use ofappropriate locking devices or specially designed prostheses.

Moreover, when the crural portion of the prosthesis performs rotativemotion along with the foot with respect to the axis of the knee-jointmechanism, an increase in the functional length of the prosthesis occursat the moment of its transfer over the bearing surface. This factnecessitates the reduction of the overall prosthesis length as comparedwith the unaffected lower extremity, which results in requiring anincreased consumption of the patients intrinsic energy in order to lifthis own weight when walking.

Another presently known prosthetics is a thigh prosthesis, whichincludes a thigh frame having a stumpreceiving chamber formed therein,and a crus with a foot portion which are articulated to each otherthrough two drag links and which, in turn, are through one of their endsarticulated to the distal end of the thigh frame, and with their otherends, to the proximal end of the crus so as to form a four-barpolycentered mechanism for the knee-joint unit.

One of the drag links is in contact with the distal portion of the thighframe so as to form a retainer which prevents the mechanism of theknee-joint unit from recurvation.

The thigh prosthesis of the above described design features rather highstability of the knee-joint mechanism against spontaneous swinging atthe moment of resting upon the prosthesis as compared to the previouslydiscussed prothesis, as well as some functional shortening of theoverall length of the prosthesis at the moment of its transfer over thebearing surface which permits the prosthesis to be made equal in lengthto the polycenter mechanism of the knee-joint unit, suffers from thedisadvantage in that it has no direct and back coupling between theprosthesis members and the patient, thereby causing uncontrolled motionof the crural portion of the prosthesis during walking, as well asproviding for inadequate stability against spontaneous swinging. Such aprosthesis, like one having a singlearticulation knee-joint mechanism,features asymmetrical motion of the prosthesis with respect to theunaffected extremity, which may be explained as follows:

Weight characteristics of the prosthesis crural portion entail aconstant value for each particular case; consequently, the moment ofmass inertia with respect to the axis of the knee-joint mechanismlikewise remains a constant value.

Oscillating motion performed .about the axis of the knee-joint mechanismgives rise to forces of inertia which provoke rotative motion of thecrus in a direction opposite to that of the thigh frame motion. Angulardisplacement of the crus will increase in a direct proportion with theamplitude and in an inverse pro-' portion with the period of oscillationof the thigh frame. This fact causes some lagging behind in the phase ofmotion of the crus with respect to the thigh frame, and an increasedperiod of oscillation of the crus forwardly from its rear-most position.

The braking and knee-folding devices which are used in the knownprostheses in order to diminish the flexural angle of and the period ofoscillation of the crus, are subject to their own inherentdisadvantages.

The frictional force in the braking devices, which proves to be ratherconstant for each particular case, is oppositely directed with respectto the forces of inertia and gravitational forces of the crural portion(i.e.,

crus-and-foot assembly) of the prosthesis, thus decreasing the angle ofdeflection of the crural portion with respect to the thigh frame, whileat the same time increas ing the period of its forward oscillations.

Elastic forces of the knee-folding devices impede the action of theforces of inertia and exert a further influence tending to decrease theangle of the flexural crus, but also in cooperation with thegravitational forces of the crus, these forces diminish the period ofoscillation of the latter and concurrently cause an increase in theangular velocity and angular acceleration, whose maximum value occurswhen the crus assumes its extreme front position and the prosthesis iscompletely extended in the knee-joint mechanism. This fact causes thegeneration of increased dynamic loads which act upon the patients stump,thus adding to arrhythmia of prosthesis-aided walking.

Thus, forces of friction generated in the braking devices and elasticforces produced by the knee-folding devices, though decreasing theflexural angle of the crus, at the same time add to load forces whichare applied to the thigh stump during the transfer of the prosthesisover the bearing surface, so as to cause an increased consumption of thepatients intrinsic energy.

Provision of passive coupling between the thigh frame and the prosthesiscrural portion makes it impossible to actively influence the motionalbehaviour of the crus in conformance with the rhythm and character ofwalking.

The presence of a second degree of freedom in the patient-prosthesissystem along with the absence of a direct and back coupling of thepatient to the kneejoint mechanism of the prosthesis requires thepatient to exercise constant control over the motion of the prosthesismembers causing further expenditures of the patients intrinsic energyfor effecting the coordination of all of the motions which are performedby the members of the patient-prosthesis during walking.

It is therefore an essential object of the present invention to providea thigh prosthesis which will enable the patient to actively control themotion of the knee-joint mechanism of the prosthesis and ensure the backcoupling of that mechanism with the patient.

The foregoing object is attained due to the fact that in a thighprosthesis, comprising a thigh frame accommodating a stump-receivingchamber, and a crus with a foot, the crus is interconnected with thethigh frame through a knee-joint mechanism possessing one degree offreedom and which is provided with a retainer for protecting the kneejoint from recurvation, according the invention, the stump-receivingchamber is made of a stump-receiving sleeve which is articulated to thethigh frame so as to be free to swing or oscillate in the sagittalplane, and is kinematically associated with the knee-joint mechanism ina manner whereby each position of the stump-receiving sleeve withrespect to the thigh frame corresponds to a defmite position of thecrus.

In the thigh prosthesis, wherein the knee-joint mechanism is made as asingle-pivot articulated joint interconnecting the thigh frame and thecrus, the kinematic association of the stump-receiving sleeve with theknee-joint mechanism is expediently formed of a link having one endthereof articulated to the movable distal end of the stump-receivingsleeve, while the other end is connected to an additional arm held inposition on the crus, whereby forward motion of the distal end in thesagittal plane with respect to the thigh frame corresponds to theflexure of the prosthesis.

In the thigh prosthesis, wherein the knee-joint mechanism comprises twodrag links forming along with the thigh frame and the crus a four-barmechanism, the kinematic association of the stump-receiving sleeve withthe knee-joint mechanism is expediently formed of a link having one endthereof articulated to the movable distal end of the stump-receivingsleeve, while the other end is connected to an additional arm held inposition on the front drag link of the four-bar knee-joint mechanism andforming a double-arm lever together with said drag link, whereby forwardmotion of the distal end in the sagittal plane with respect to the thighframe corresponds to the flexure of the prosthesis.

It is desirable that the link interconnecting the distal end of thestump-receiving sleeve with the double-arm lever be spring-loaded withrespect to the stumpreceiving sleeve in the direction of the prosthesisextension.

Walking with such prostheses involves minimum consumption of thepatients intrinsic energy, while the biomechanics of walking are closeto normal, i.e., the pa rameters of motion of all the prosthesis membersare identical with those of the unaffected extremity, irrespective ofthe rhythm and character of walking.

The inventive prostheses are also more functional as compared to theprior art prosthesis.

The herein-disclosed thigh prostheses are essentially linkage-typemechanisms enabling a biomechanical train of members possessing onedegree of freedom to be obtained in the system so-calledpatientprosthesis, system as well as providing for a direct and backcoupling between the patient and the artificial extremity, andconcurrently controlled motion of its knee-joint mechanism. Provision of1 of freedom enables the prosthesis, with any two members thereofdead-fixed to each other, to be, in effect a static support possessingzero degree of mobility.

Movable connection between the stump-receiving sleeve and the thighframe reduces the amplitude of oscillation of the common center ofgravity of the prosthesis in the vertical plane and the amplitude ofconstrained oscillation of the thigh frame in the sagittal plane, whichis conducive to a reduced consumption of the patients intrinsic energygenerally spent for moving the prosthesis forwardly during walking.

In the following description the invention is considered in detail byway of exemplary embodiments thereof, taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a diagrammatic representation of a thigh prosthesisincorporating a knee-joint mechanism made as a single-pivot articulatedarrangement, according to the invention;

FIG. 2 is the prosthesis of FIG. 1 in one of its dynamic positions;

FIG. 3 is a second embodiment of a thigh prosthesis having a four-barknee-joint mechanism, according to the invention; and

FIG. 4 is the prosthesis of FIG. 3 in one of its dynamic positions.

Reference is now had to FIGS. 1 and 2, in which the thigh prosthesis ofthe invention comprises a stumpreceiving sleeve 1, having wherein astump-receiving chamber formed therein, a thigh frame 2, both beinginterconnected through two articulated joints 3 which are respectivelylocated on the medial and lateral sides of the stump-receiving sleeve 1,and .a crus 4 with a foot portion.

An optimum portionof location of the joints 3 on the stump-receivingsleeve 1 is the level of a natural hip joint, whereas the optimumposition of installation of the joints 3 in constructing the prosthesisis the level of the proximal edge of the stump-receiving sleeve 1 on themedial side thereof. When using self-aligning bearings or those withfloating inner races as the joints 3, the latter may be located on thelateral side somewhat more proximate than the joint 3 on the medial sideof the stump-receiving sleeve 1.

TI-le thigh frame 2 and the crus 4 are interconnected by means of asingle-pivot joint 5 which is, in effect, the knee-joint mechanism ofthe prosthesis. The stumpreceiving sleeve 1, the thigh frame 2, thejoint 5, and the crus 4 with the foot, collectively form the bearingframe of the prosthesis.

The stump-receiving sleeve 1 in its distal portion has a joint 6, towhich a link 7 is connected at one of its ends, and a seat whichaccommodates a damper 8.

The crus 4 has an arm 9 located on the rear surface of the proximalportion so as to thereof form a doublearm lever therewith. The other endof the link 7 is connected to the arm 9 by means of an articulated joint10.

An alternative way of connecting the distal end of the stump-receivingsleeve 1 to the proximal end of the crus 4 may involve, for example, anyother kinematic pair, such as a gear train (not shown) instead of thelink 7.

The link 7 is spring-loaded with respect to the stump receiving sleeve 1by means of an elastic member 10 which comprises, for example, a spring,so as to be biased in the direction of the prosthesis extension.

The tension of the elastic member 10 is adjusted when fitting theprosthesis so as to suit the weight data of the crus 4 and the characterof the patients gait. When in a static position, the tension of theelastic member 10 should be minimal.

The thigh frame 2 is provided with a retainer 11 which is adapted tointeract with a damper 12 mounted in the proximal portion of the crus 4so as to protect the knee joint from recurvation.

In order to provide increased stiffness, the frame 2 is fitted with asemi-ring 13 which, at the same time, performs the functions of arestrictor for the stumpreceiving sleeve 1 to thereby limit its backwardrotation with respect to the frame 2. From externally thereof themechanism of the prosthesisis lined with an elastic material to therebyfollow the shape and size of the patients unaffected extremity.

The present thigh prosthesis, as shown in FIGS. 3 and 4, may also have aknee joint incorporating two drag links 14 and 15 (FIGS. 3, 4) whichform, along with a thigh frame 16 and a crus 17, a four-bar knee-jointmechanism. A stump-receiving sleeve 18 of that prosthesis which includesa stump-receiving chamber, is connected to the thigh frame 16 via twoarticulated joints 19 similar to the joints 3 of the thigh prosthesisrepresented in FIGS. 1 and 2.

The front drag link 14 (FIGS. 3, 4) of the four-bar knee-joint mechanismis provided with an extra arm 20 so as to form, along with the drag link14 a double-arm lever.

The arm 20 of the double-arm lever'is articulated through a link 21 tothe movable distal end of the stump-receiving sleeve 18.

The stump-receiving sleeve 18, the thigh frame 16, the drag link 14 withthe arm 20, the drag link 15 and the crus 17 with the foot, collectivelyform the bearing frame of the prosthesis.

A retainer 22 is provided on the drag link 14 of the knee-jointmechanism in order to interact with a damper 23 on the thigh frame 16 tothereby prevent the knee joint from recurvation.

The link 21 is spring-loaded with respect to the stump-receiving sleevein the direction of the prosthesis extension through an elastic member24.

The tension of the elastic member 24, as well as the tension of theelastic member 10 (FIG. 1), is adjusted when fitting the prosthesis soas to suit any particular patient.

The thigh frame 16 (FIG. 3) has a semi-ring 25 which adds to thestiffness thereof and also serves tO restrict backward motion of thestump-receiving sleeve 18 with respect to the frame 16.

If the prosthesis is to be used for children or juvenile patients, thecrus 4 (FIG. 1) and the crus 17 (FIG. 3) may be made extensible.

The prosthesis may be attached to the patients stump by any conventionalmethod such as, say, vacuum valves, binder or waist hangers, and thelike.

The present thigh prosthesis functions as follows:

The stump-receiving sleeve 1 (FIG. 1) is capable of performingcontrolled oscillating motion with respect to the frame 2 With thefulcrum at the joints 3, the motion being established as a result of theinteraction of the active forces of the stump, the gravitational forcesof the prosthesis members, and the forces of inertia.

The active forces of the stump are variable both as to magnitude anddirection, and their parameters are under the control of the patientscentral nervous systern. The gravitational forces of the prosthesismembers have a constant magnitude for each particular case so that,consequently, the moment of inertia of the mass center about the axis ofthe knee-joint mechanism is maintained constant.

When the stump-receiving sleeve 1 turns forward with respect to thethigh frame 2 in the sagittal plane, its distal end imparts motion tothe link 7 so as to cause the crus 4 to turn in the opposite directionin correspondence with the flexure of the prosthesis.

Thus, rotation of the stump-receiving sleeve 1 in the sagittal planeresults in the turning of the crus 4, and corresponding theretdboth inmagnitude and direction.

The elastic member 10, as the flexural angle of the knee-joint mechanismbecomes larger, brakes the rotary motion of the crus 4 and thestump-receiving sleeve 1, thus acquiring some amount of energy forimparting forward rotation to the crus 4.

' Under the action of the active forces of the stump, of the elasticmember 10 and of gravitational forces of the prosthesis members, thecrus 4 performs forward rotary motion, thereby expecting its extension.

The damper 8, during the prosthesis extension, interacts with the crus 4to provide smooth contact between the retainer 11 with the damper 12,both fixing the position of the crus 4 with respect to the frame 2, andthereby preventing recurvation of the knee-joint mechanism. When thedamper 8 is compressed, there occurs further backward motion of thedistal end of the stumpreceiving sleeve 1, so as to cause furtherforward rotation of the crus 4, thus precluding the prosthesis frombeing flexed during the supporting phase of the pace and rendering theprosthesis a stable static support capable of taking up compressive andbending stresses.

As a result of elastic strain, the damper 8 acquires some quantity ofenergy so as to release the stationary position of the prosthesis at themoment it is raised over the bearing surface in the following phase ofthe pace. Moving the prosthesis out of its stationary state results fromthe interaction of the active stump forces and the elastic forces of thedamper 8, with a minimal consumption of the patients intrinsic energy.

Thus, the patient is in an active interaction with the stump-receivingsleeve 1 and further, via the thigh frame 2, the link 7 and the elasticmember 10 he exercises direct coupling with the knee-joint mechanism ofthe prosthesis, thus ensuring controlled motion of the crural portion ofthe prosthesis, viz., the crus 4 with the foot, while walking so as torender it possible for the patient to approximate the parameters ofmotion of the prosthesis with those of the unaffacted extremity at anyrythm and charater of gait.

Back coupling of the prosthesis with the patient is effected by virtueof the action of the stump-receiving sleeve whose position correspondsto a definite position of the knee-joint mechanism with respect to, thepatients stump.

The knee-joint mechanism of such a prosthesis increases the functionallength of the prosthesis when the latter is transferred over the bearingsurface, which necessitates an increase in the overall length of theprosthesis within 1 cm.

This fact requires some of the patients intrinsic energy to be consumedfor raising his own weight and to some extent disturbs the patients gaitfrom the viewpoint of cosmesis, causing a somewhat increased rocking otthe patients body in the vertical plane during walking. Nevertheless,high stability margin is ensured by the prosthesis for its knee-jointmechanism so as to involve but a minimum consumption of the patientsintrinsic energy during walking, through which account the prosthesismay be recommended for children or elderly patients, as well as forpatients in a weak physical state of health.

When the stump-receiving sleeve 18 of the prosthesis shown in FIGS. 3and 4, rotates in the forward direction with respect to the high frame16 its distal end imparts rotary motion via the connection link 21 tothe doublearm lever constituted by the drag link 14 and the the arm 20which, in turn, causes the crus 17 to turn in a direction opposite tothat of motion of the stumpreceiving sleeve 18 with the result that thedrag link moves and the prosthesis flexes in its knee-joint mechanism.

Thus, rotation of the stump-receiving sleeve 18 causes displacement ofthe drag links 14 and 15 together with the crus 17, to an extent whichis equal in magnitude and opposite in direction.

The elastic member 24, as the flexural angle of the prosthesis increasesin the knee-joint mechanism, brakes the rotary motion of the drag link14 and the crus 17, thus acquiring an amount of energy so as to impartreverse rotary motion (i.e., forward) to the crus 17 and the drag link14. The elastic member 24 renders smooth the rotary motion of the crusl7 smooth at the final stage of the flexure of the prosthesis as well asensuring timely delivery of a force impulse for the crus to enable thelatter to perform rotary return motion with respect to the thigh frame16 in a forward direction.

The damper 23, .during the final stage of the prosthesis extensi o n,intera cts vvith the retainer 22 so as to ensure smooth contact betweenthe crus 17 and the thigh frame 16 and to fix the position of the formerrelative to the latter, thus preventing the knee-joint mechanism fromrecurvation.

Backward motion of the distal portion of the stumpreceiving sleeve 1depends upon the degree of compression of the damper 23. Optimum angularparameters between the stump-receiving sleeve 18, the link 21 and thedrag line 14 ensure the stable position of the knee-joint mechanismduring the supporting phase of the pace, thus rendering the prosthesisto be held in a stable support which is capable of bearing compressiveand bending loads.

As a result of elastic strain, the damper 23 acquires some amount ofenergy to release the stable position of the knee-joint mechanism at themoment when the prosthesis is raised above the bearing surface (at thefinal supporting phase of the pace), for enabling performance of thenext phase of the pace.

Moving the knee-joint mechanism out of a stable position is effected dueto the interaction of the active stump forces and the elastic forces ofthe damper 23 at a minimum consumption of the patients intrinsic energy.

The construction of the polycenter knee-joint mechanism of theherein-disclosed prosthesis provides for functional shortening of theoverall prosthesis length which is effective within the phase oftransferring the prosthesis over the bearing surface. This fact makes itpossible to obtain an artificial extremity equal in its overall lengthto an unaffected leg.

The identity of the overall data decreases the oscillation amplitude ofthe patients common center of gravity in the vertical plane whichexcludes any expenditures of the patients intrinsic energy for raisinghis own weight during walking.

The patient is in an active interaction with the stumpreceiving sleeve18 and further, via the link 21 and the drag link 14 he exercises directcoupling with the kneejoint mechanism and ensures controlled motion ofthe prosthesis crural portion (viz., the crus 17 along with the foot)during walking so as to suit the rhythm and character of his gait, thusapproximating the parameters of the prosthesis motion to those of theunaffected extremity.

Through mechanical exertion upon the patients stump, the patientreceives signals informing him of the operation of the knee-jointmechanism, so as to provide for a back coupling of the artificialextremity with the living organism.

The proposed prosthesis may be recommended for use by the patients ofall age groups, both male and female, irrespective of their healthstate, but with due allowance for medical indications.

Both the prosthesis shown in FIG. 1 and illustrated in FIG. 3 may beused in pairs with prosthesis of any other type (in case of bilateralamputation of extremities).

What is claimed is:

l. A thigh prosthesis, comprising: a thigh frame; a crus having a footportion; a knee-joint mechanism possessing one degree of freedom ofmovement connecting said crus to said thigh frame; a retainer protectingsaid knee-joint mechanism from recurvation; a stumpreceiving sleevehaving a stump-receiving chamber, said sleeve being kinematicallyfastened to said kneejoint mechanism and articulated to said thigh frameto permit oscillation of the former in the sagittal plane, said sleevebeing fastened to said knee-joint mechanism so that each position ofsaid stump-receiving sleeve with respect to said thigh frame correspondswith a particular position of said crus, said knee-joint mechanismcomprising a single-pivot joint interconnecting said crus and said thighframe; arm means retained in position on said crus so as to form adouble arm therewith; and a link articulately interconnecting said armmeans and a distal end of said stump-receiving sleeve, said linkimparting kinematic movement between the stumpreceiving sleeve and theknee-joint mechanism whereby forward motion of said distal end of thestump-receiving sleeve in the sagittal plane with respect to said thighframe corresponds to a flexure of the prosthesis.

2. A thigh prosthesis as claimed in claim 1, comprising spring meansconnected to said link for biasing the latter with respect to saidstump-receiving sleeve in the direction of extension of the prosthesis.

3. A thigh prosthesis; comprising: a thigh frame; a crus having a footportion; a knee-joint mechanism possessing one degree of freedom ofmovement connecting said crus to said thigh frame; a retainer protectingsaid knee-joint mechanism from recurvation; a stumpreceiving sleevehaving a stump-receiving chamber, said sleeve being kinematicallyfastened to said knee- 5 joint mechanism and articulated to said thighframe to permit oscillation of the former in the sagittal plane, saidsleeve being fastened to said knee-joint mechanism so that each positionof said stump-receiving sleeve with respect to said thigh framecorresponds with a particular position of said crus, said knee-jointmechanism comprising two drag links forming a four-bar knee-jointmechanism with said thigh frame and said crus, arm means mounted in aposition on the front of one of said drag links and forming a double-armlever with said one drag link; a connecting link articulatelyinterconnecting a movable distable end of said stump-receiving sleeveand said arm means so as to impart kinematic movement between saidstump-receiving sleeve and said knee-joint mechanism whereby forwardmotion of said distal end of the stump-receiving sleeve in the sagittalplane with respect to said thigh frame corresponds to a flexure of theprosthesis.

4. A thigh prosthesis as claimed in claim 3, comprising spring meansconnected to said connecting link for biasing the latter with respect tosaid stump-receiving sleeve in the direction of extension of theprosthesis.

1. A thigh prosthesis, comprising: a thigh frame; a crus having a footportion; a knee-joint mechanism possessing one degree of freedom ofmovement connecting said crus to said thigh frame; a retainer protectingsaid knee-joint mechanism from recurvation; a stump-receiving sleevehaving a stump-receiving chamber, said sleeve being kinematicallyfastened to said knee-joint mechanism and articulated to said thighframe to permit oscillation of the former in the sagittal plane, saidsleeve being fastened to said knee-joint mechanism so that each positionof said stumpreceiving sleeve with respect to said thigh framecorresponds with a particular position of said crus, said knee-jointmechanism comprising a single-pivot joint interconnecting said crus andsaid thigh frame; arm means retained in position on said crus so as toform a double arm therewith; and a link articulately interconnectingsaid arm means and a distal end of said stump-receiving sleeve, saidlink imparting kinematic movement between the stump-receiving sleeve andthe knee-joint mechanism whereby forward motion of said distal end ofthe stumpreceiving sleeve in the sagittal plane with respect to saidthigh frame corresponds to a flexure of the prosthesis.
 2. A thighprosthesis as claimed in claim 1, comprising spring means connected tosaid link for biasing the latter with respect to said stump-receivingsleeve in the direction of extension of the prosthesis.
 3. A thighprosthesis; comprising: a thigh frame; a crus having a foot portion; aknee-joint mechanism possessing one degree of freedom of movementconnecting said crus to said thigh frame; a retainer protecting saidknee-joint mechanism from recurvation; a stump-receiving sleeve having astump-receiving chamber, said sleeve being kinematically fastened tosaid knee-joint mechanism and articulated to said thigh frame to permitoscillation of the former in the sagittal plane, said sleeve beingfastened to said knee-joint mechanism so that each position of saidstump-receiving sleeve with respect to said thigh frame corresponds witha particular position of said crus, said knee-joint mechanism comprisingtwo drag links forming a four-bar knee-joint mechanism with said thighframe and said crus, arm means mounted in a position on the front of oneof said drag links and forming a double-arm lever with said one draglink; a connecting link articulately interconnecting a movable distableend of said stump-receiving sleeve and said arm means so as to impartkinematic movement between said stump-receiving sleeve and saidknee-joint mechanism whereby forward motion of said distal end of thestump-receiving sleeve in the sagittal plane with respect to said thighframe corresponds to a flexure of the prosthesis.
 4. A thigh prosthesisas claimed in claim 3, comprising spring means connected to saidconnecting link for biasing the latter with respect to saidstump-receiving sleeve in the direction of extension of the prosthesis.